HackSkills is an organized knowledge base of installable skills that gives AI agents practical security knowledge across areas such as web security, privilege escalation, reverse engineering, and digital forensics. It is intended for bug bounty work, penetration testing, CTF competitions, and authorized security research. The catalogue entries are the project's own master, category, and topic skills.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add yaklang/hack-skills --skill upload-insecure-filesgit clone --depth 1 https://github.com/yaklang/hack-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/yaklang/hack-skills/upload-insecure-files)<a href="https://agentmods.dev/skills/yaklang/hack-skills/upload-insecure-files"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/upload-insecure-files.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00037 | $0.04565 |
| Opus 5 | $0.00018 | $0.02282 |
| Sonnet 5 | $0.00007 | $0.00913 |
| Haiku 4.5 | $0.00004 | $0.00456 |
Grade C, and why
upload-insecure-files scanned grade C with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Cloud metadata endpointhighServer-side request forgery
One request to 169.254.169.254 can return temporary IAM credentials.
http://169.254.169.254/latest/meta-data/iam/security-credentials/ Copies of this mod
3 near-identical copies found in the catalogue:
- upload-insecure-files — 100% identical, 0 lines differ
- upload-insecure-files — 100% identical, 0 lines differ
- upload-insecure-files — 92% identical, 4 lines differ
How it starts
The opening of the file, as written. The whole thing — 543 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: Upload Insecure Files — Validation Bypass, Storage Abuse, and Processing Chains
AI LOAD INSTRUCTION: Expert file upload attack playbook. Use when the target accepts files, imports, avatars, media, documents, or archives and you need the full workflow: validation bypass, storage path abuse, post-upload access, parser exploitation, multi-tenant overwrite, and chaining into XSS, XXE, CMDi, traversal, or business logic impact. For web server parsing vulnerabilities, PUT method exploitation, and specific CVEs (WebLogic, Flink, Tomcat), load the companion SCENARIOS.md.
0. RELATED ROUTING
Extended Scenarios
Also load SCENARIOS.md when you need:
- IIS parsing vulnerabilities —
x.asp/directory parsing,;semicolon truncation (shell.asp;.jpg) - Nginx parsing misconfiguration —
avatar.jpg/.phpwithcgi.fix_pathinfo=1 - Apache parsing — multiple extensions,
AddHandler, CVE-2017-15715\n(0x0A) bypass - PUT method exploitation — IIS WebDAV PUT+COPY, Tomcat CVE-2017-12615
readonly+.jsp/bypass - WebLogic CVE-2018-2894 arbitrary file upload via Web Service Test Page
- Apache Flink CVE-2020-17518 file upload with path traversal
- Upload + parsing vulnerability chain — EXIF PHP code + Nginx
/.phppath info - Full extension bypass reference table (PHP/ASP/JSP alternatives, case variations, null bytes)
Use this file as the deep upload workflow reference. Also load:
- path traversal lfi when filename, extraction path, or include path becomes file-system control
- xss cross site scripting when uploads are rendered in browser contexts
- xxe xml external entity when SVG, OOXML, or XML imports are accepted
- cmdi command injection when a processor, converter, or media pipeline executes system tools
- business logic vulnerabilities when quotas, overwrite rules, approvals, or storage paths create logic bugs
- ghost-bits-cast-attack when the server is Apache Tomcat and the WAF blocks
.jspinfilename*— Tomcat'sRFC2231Utilitynarrows each char to byte, so1.陪sp(U+966A low byte =j) writes1.jspto disk while the WAF sees no.jspliteral
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 3d ago First seen · 543 lines · 37 tokens per session scan C 543343d08d49
upload-insecure-files is a skill published in the GitHub repository yaklang/hack-skills (2,098 stars, last pushed 2mo ago), licensed MIT. It adds 37 tokens to every session and 4,565 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it C with 1 finding (cloud metadata endpoint). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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